In the production of hydrocarbons from underground formations located in Alaska, Canada, Peru, Indonesia, and any region where ground transportation is restricted or non-existent during all or part of the year, and in drilling for oil from offshore locations, and in remote jungle locations, it often becomes necessary to transport by air the materials and equipment needed to drill and explore for the oil.
Due to the cumbersome size and weight of the equipment comprising the average drilling rig, much of the rig must be tediously disassembled piece-by-piece and flown in by large air transport. This normally requires disassembly of the heavy chain drive units, the final drive unit, and the drawworks for movement to the drilling site. This requires a timely and expensive reassembly at the site with a complicated realignment of the reassembled machinery. It often necessitates disassembly of each of the chain case assemblies which means draining of the oil and extensive protection to prevent contamination of the chains and sprockets with dirt, water, and other debris. Then the chain cases must be reassembled on site, often a task near impossible in subzero blizzard conditions or during heaving storms at sea.
Even though the art has progressed enough to place many individual components each on their own portable skid, these must be moved by ship to offshore locations or by large air transport to northern regions because of their extreme weight.
When weather condtions or lack of roads and airfields prevent the use of ships or airplanes, the driller must resort to helicopter transportation of the rigs which requires that each of the usual skid packages must be broken down even further due to the relatively light carrying capacity of the helicopters available. This cancels the portability advantage of the normal skid units since reassembly of their components requires almost as much time as that of the older rigs did.
The present invention overcomes the limitations of the prior devices by providing a drilling rig compound comprised entirely of subcomponents each of which is an integral package transportable by helicopter and easily assimilated together to form a drilling rig of any desirable size or capacity. Each subcomponent is fully portable and is below the maximum weight transportable by helicopter, and each subcomponent is easily joined with the others without lengthy adjustment or realignment needed. In the present invention, the chain drive assemblies, often termed chain cases, are integral, sealed units each helicopter transportable without requiring any disassembly of the chains or sprockets from the cases. Also the final drive assembly utilizes a split transmission drive, with each transmission being an integral unit which is helicopter transportable. The drawworks also utilizes a drum drive and brake assemblies which can be broken up into separate transportable units capable of quick reconnection on site without need for alignment or adjustment.